Don't worry, they will let the community know when this tool is ready.

http://www.neondragon.net/viewtopic.php?p=489580#p489580 wrote:Cash/Stats transfer from non steam to Steam accounts
We have decided that we are going to allow anyone who switched from playing non steam to steam, to transfer his stats and cash over to his new steam account. This will only be available one time for each person under the criteria that they are able to prove that the non steam ID provided is their own. However this will not be available until we have gotten the correct tools in place. A separate topic will then be made where you can request stat/cash transfer.

There hasn't been many updates on the situation of the tool, but it seems like it won't be added before August.
But there's no set date for it.
So I won't say "It'll be added...". It's just not likely that it'll be added before August.